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T Jenkins

Publications and source records attributed to T Jenkins.

At least 109 records · Page 6Linked to original sources
PubMed1992

The Y-associated XY275 low allele is not restricted to indigenous African peoples.

The level of linkage disequilibrium between the XY275 MspI polymorphism and the X and Y boundaries was investigated in 21 different southern African populations. A full range of frequencies of the high allele was observed on the 1,013 X chromosomes studied, in keeping with published data. In previous studies fixation of the high allele on the Y chromosome was observed in all but two groups--a Pygmy and a Tsumkwe San population. However, in the present study of 673 Y chromosomes, the low allele was found to be associated with the Y chromosome in several different Bantu-speaking negroid groups, the Khoisan-speaking negroid Dama, the Khoisan, two groups of mixed ancestry, and the South African Asiatic-Indian population. The discovery of the low allele on Y chromosomes of caucasoid individuals suggests that more than one class of Y chromosome gave rise to the present-day non-African population. The data also fail to provide support for the theory that Africa is the site of origin of Homo sapiens, but they equally do not exclude it.

Africa, Southern↗
PubMed1992

Cystic fibrosis. Part II. New developments in cystic fibrosis--implications for carrier detection and genetic counselling.

Cystic fibrosis (CF) is an autosomal recessive disorder found predominantly in people of European origin. Prenatal diagnosis for this disorder is now possible using the polymerase chain reaction technique to detect the most common CF-causing mutation, delta F508. Case studies of prenatal diagnosis and carrier detection are presented and some of the genetic counselling issues related to these investigations are discussed.

Cystic Fibrosis↗
PubMed1992

Cystic fibrosis. Part I. Frequency of the delta F508 mutation in South African families with cystic fibrosis.

Cystic fibrosis (CF) is a common autosomal recessive disorder among people of European origin. With the localisation of the gene locus to chromosome 7q31 and the identification of closely linked polymorphic markers in 1985, it became possible to offer prenatal testing to couples at risk of having CF children, provided a live affected individual from that family was available for investigation. The CF gene, named CFTR, was cloned and sequenced in 1989 and the most common CF-causing mutation, delta F508, identified. A search for this mutation has been carried out in 81 South African white CF families of European origin. Using the polymerase chain reaction (PCR) technique the frequency of delta F508 was found to be 0.81. This mutation was not found in the 1 negroid and the 1 Indian CF family investigated.

Amniocentesis↗
PubMed1992

Y chromosome probe p49a detects complex PvuII haplotypes and many new TaqI haplotypes in southern African populations.

Y-specific 49a/TaqI haplotypes were determined for 831 individuals drawn from 21 different southern African populations. A total of 31 new haplotypes were observed, some of which contained new alleles or allelic variants. Duplication, in addition to CpG mutation, is implicated in the generation of certain allelic variants. Cluster analysis of genetic distances between the populations, calculated using the 49a/TaqI haplotype frequencies, revealed a basic split between African and non-African populations. Hybrid groups cluster with the caucasoid groups, indicating that male gene flow has occurred from the latter into the former. Clustering of the negroid and Khoisan groups is not what might have been expected from the known linguistic affinities. It is suggested that the 49a/TaqI haplotype analysis of these populations is not sufficiently sensitive to distinguish between many of the populations. The Y-specific 49a/PvuII polymorphism was studied in 127 individuals from southern African populations, and 17 polymorphic fragments ranging in size from 3.6 kb to greater than 48 kb were identified. A total of 53 PvuII haplotypes were observed, corresponding to only 30 TaqI haplotypes. There appears to be poor correlation between the two polymorphisms.

Africa, Southern↗
PubMed1991

Prenatal diagnosis for Huntington's disease: a molecular and psychological study.

Two linked probes were used to determine the Huntington's disease status of the fetus conceived by a woman affected with the condition. The fetus was found to be unaffected with a certainty of 97 per cent. The ethical issues associated with presymptomatic testing were avoided since the mother presented with initial symptoms of Huntington's disease, but other psychological and ethical issues arose. The concerns of an affected woman planning a pregnancy, and the dilemmas involved in decision-making regarding prenatal diagnosis and possible selective abortion were exposed and explored with the patient and her husband.

Adult↗
PubMed1991

The structure of human mitochondrial DNA variation.

Restriction analysis of mitochondrial DNA (mtDNA) of 3065 humans from 62 geographic samples identified 149 haplotypes and 81 polymorphic sites. These data were used to test several aspects of the evolutionary past of the human species. A dendrogram depicting the genetic relatedness of all haplotypes shows that the native African populations have the greatest diversity and, consistent with evidence from a variety of sources, suggests an African origin for our species. The data also indicate that two individuals drawn at random from the entire sample will differ at approximately 0.4% of their mtDNA nucleotide sites, which is somewhat higher than previous estimates. Human mtDNA also exhibits more interpopulation heterogeneity (GST = 0.351 +/- 0.025) than does nuclear DNA (GST = 0.12). Moreover, the virtual absence of intermediate levels of linkage disequilibrium between pairs of sites is consistent with the absence of genetic recombination and places constraints on the rate of mutation. Tests of the selective neutrality of mtDNA variation, including the Ewens-Watterson and Tajima tests, indicate a departure in the direction consistent with purifying selection, but this departure is more likely due to the rapid growth of the human population and the geographic heterogeneity of the variation. The lack of a good fit to neutrality poses problems for the estimation of times of coalescence from human mtDNA data.

Alleles↗
PubMed1991

Utility of Leopold maneuvers in screening for malpresentation.

Malpresentation is a common complication of pregnancy. Using ultrasound as the gold standard, we prospectively tested Leopold maneuvers as a screen for nonvertex presentation in the third trimester. In our hands this technique performed poorly. Values for sensitivity, specificity, positive predictive value, and negative predictive value were 28, 94, 24, and 95%, respectively, in a population with a 7% prevalence of noncephalic presentation. Much of the correlation between the screening and diagnostic tests seemed to arise from chance (kappa = 0.13).

Breech Presentation↗
PubMed1991

Catecholamine levels in pregnant physicians and nurses: a pilot study of stress and pregnancy.

As a pilot study of occupational stress and pregnancy, we measured urinary catecholamine excretion in ten pregnant physicians and three intensive care nurses between 26-37 weeks' gestation, once during a work day and again during a non-work day. Urinary catecholamines were increased by 58% (P less than .03) during work periods compared with non-work periods. Catecholamine levels were also increased by 64% (P less than .025) over those of a working non-physician control group of similar gestational age. Urinary catecholamine levels are a direct reflection of plasma catecholamine levels. Catecholamine levels are known to increase with physical stress, such as standing, and with mental stress, such as difficult problem-solving. Catecholamines are also known to decrease uterine blood flow. Measurement of catecholamines may be a helpful marker in investigating the relationship between occupation and pregnancy outcome.

Catecholamines↗
PubMed1990

Genetic and physical mapping and population studies of a fibronectin receptor beta-subunit-like sequence on human chromosome 19.

A cDNA clone of the beta subunit of human fibronectin receptor (FNRB) detects two different polymorphic loci: (a) a codominant system previously mapped to the pericentromeric region of chromosome 10, the site of the functional FNRB gene; and (b) a dominant system not linked to the first one or to any chromosome 10 marker tested. This second polymorphism is characterized by the presence or absence of a band (or a set of bands). We have used linkage analysis and biotin-labeled in situ hybridization to map this dominant polymorphism to the short arm of chromosome 19; we hypothesize that it may be due to the insertion of part of the cDNA from the chromosome 10 gene into chromosome 19. This "insertion" is polymorphic in all populations studied.

Chromosome Mapping↗
PubMed1990

Phenotypic expression of the HLA linked iron-loading gene in males over the age of 40 years: a population study using serial serum ferritin estimations.

The frequency of the HLA linked iron-loading gene was assessed in 1783 Afrikaner men over the age of 40 years living in the South Western Cape. Measurements, made on three occasions over a 4.5 year period, included the serum ferritin concentration, a screening test for reduced unsaturated iron-binding capacity and the percentage transferrin saturation. The serum gamma-glutamyl transferase concentration was used as a marker of alcohol abuse. The diagnosis of homozygosity was based on a serum ferritin concentration that was persistently greater than 400 micrograms l-1 and a percentage transferrin saturation greater than 55%. Using these criteria, 17 subjects were diagnosed as homozygous, corresponding to a disease frequency of 0.0095, a gene frequency of 0.0976 and a heterozygote frequency of 0.176 (95% confidence limits: 0.135-0.213). None of the subjects had overt clinical haemochromatosis. Typing for the HLA-A, -B, -C and -DR loci showed that the HLA-A3 allele (frequency 0.6471 and relative risk 4.4) was the only independent marker for the iron-loading gene in this asymptomatic population. Using the present approach it was not possible to distinguish between heterozygotes, alcohol abusers and normal subjects with serum ferritin concentrations at the upper end of the normal range.

Adult↗
PubMed1990

In quest of the tyrosinase-positive oculocutaneous albinism gene.

The gene which causes tyrosinase-positive oculocutaneous albinism (ty-pos OCA) is not known. Forty-seven Bantu-speaking Negroid families with ty-pos OCA were studied in an attempt to find linkage to the gene. Fifteen 'classical' and seven DNA polymorphisms were used in the search for linkage. Close linkage was excluded for the Rh, Gc and beta-globin loci. There is no suggestion of linkage to MNS, ABO, PGM1, 6PGD, ACP1, GPX1, GLO1, GPT1, PEP A, Tf, alpha 1-AT, Hp, DQA, DXA and three arbitrary restriction fragment length polymorphisms (RFLPs). There is a slightly positive lod score for pAW101 (D14S1) (0.591 for theta = 0.2). An 'interesting' lod score was obtained with Bf and a haplotype generated by the markers DQA and DXA (1.575 for theta = 0.1 and 0.979 for theta = 0.2, respectively). Further testing of markers on chromosome 6p are indicated. Although ty-pos OCA in Southern Africa is likely to be a homogeneous disorder, genetic heterogeneity cannot be excluded as differences due to the presence/absence of ephelides within families have been observed. To date 57% of the genome has been excluded from linkage with ty-pos OCA.

Albinism, Oculocutaneous↗
PubMed1990

Red or rufous albinism in southern Africa.

Red or rufous albinism is a rare type of oculocutaneous albinism described, but not as yet fully investigated, in Africa and New Guinea. Twelve rufous albino subjects from 10 families participated in this preliminary study. The prevalence of rufous albinism was found to be approximately one in 8,580 among school children in the negroid population. The combination of the unusual red skin colour, ginger to reddish hair colour, low susceptibility to sun damage, and minimal visual problems, in affected individuals, suggested that they form a group which is distinct from the brown and other types of albinism. The mode of inheritance was found to be recessive. Tyrosinase assays showed that rufous albinos are tyrosinase positive and on electron microscopy studies normal melanosomes and melanocytes were observed in hair bulbs and skin. Visual evoked potential testing did not show the gross decussation abnormalities of the optic pathway detected in other types of albinism. Rufous albinism might be at one end of the spectrum of types of oculocutaneous albinism and, because affected people have such mild symptoms, their inclusion in this group might be debatable.

Adolescent↗